This invention relates to clinical chemistry analyzers, systems and methods. In particular, it relates to instruments for measuring the concentration, and changes of concentration, in a chromophore substance indicating the amount of a particular analyte present in a sample.
Different systems are known for measuring the concentration of a chromophore in samples. In one known form these instruments are based on a steady state lamp source passing a steady light beam through the sample. The steady state lamp source may use a tungsten-halogen filament. The power of such a lamp is about 50 to 100 watts and in the steady state operation from 1 to 15 minutes to upwards of 1 hour exposure to the lamp source is needed to provide an operational analytic system for the samples.
Another characteristic of some known steady state system is the use of a first light beam which passes through the sample. A second light beam is split off from the first light beam and is used as a reference beam. The two light beams are physically spatially separated. Electronic switch means exposes the detector and measuring electronics alternately, and thus not simultaneously, to measure multiple wavelengths coming from each of the beams of the steady light beam source. This is complicated, and the switching back and forth between the physically spaced beams may not provide for as precise a system as desirable.
In yet another form of known system a single set of optics is used and a reference beam followed by a sampling light beam passes alternately through the optical system. These two light beams are separated in time. When the sampling light beam is passed through, the sample is placed in the sample holder. When the reference beam is passed through, there is no sample in the holder. This procedure, therefore, is relatively cumbersome because of the need to change periodically the sample in the holder.
In another form of instrument, the incoming beam from the steady state source is split so that a small portion of the beam passes through a reference detector and upwards of 95% of the light beam passes through the sample and the detector associated with the sample. This system looks at the overall spectrum of the white light effect in determining the analysis of the sample.
These above known systems all have in common the use of the two light beams. The light measurement is of the entire white light spectrum or a particular wavelength.
Analysis to obtain a measurement of concentration of analyte is determined from a measurement of the absorbance of a chromophore which is given by the formula: ##EQU1## I refers to the intensity measured through the sample and I.sub.o refers to the intensity of the reference beam. The intensities could be of either a white light measurement or of a particular wavelength as generated by the double beam method.
Absorbance is related to the chromophore's concentration in terms of the formula: EQU Abs=Ebc
where E is the extinction coefficient which is related to an absorbability factor; b is the path length of a cell; and c is the concentration.
A characteristic requirement of known systems using a single beam is that a very high stability of the operation of the light source is necessary in order to obtain measurements with the requisite degree of precision. For effectively precise measurements it is necessary to have a high light stability in the order of about 1/10% over 1 hour. Relatively costly technology and components must be used to obtain this stability. Because of this high degree of stability, a relatively high speed operational procedure and analysis system can be used. However, as indicated, this is costly because of the components and methodology needed to obtain the high degree of light stability.
With the increasing throughput load demands for precise analysis and measurement in the medical, chemical and quantitative fields, it is becoming important to provide for high speed measurements on system containing multiple samples with precision.
Currently known systems do not provide a fast enough throughput with sufficient precision, and at an acceptably relatively lower cost. There is a need to provide systems which can immediately provide analyses of multiple samples.